Update source/release-notes.txt

Co-authored-by: Sarah Olson <[email protected]>

Author: ianf-mongodb

source/release-notes.txt

@@ -26,7 +26,7 @@ Bug Fixes:
   stop or show as not started.
 - Fixes an issue where JSON columns could not be migrated if they contained 
   top-level arrays.
-- Fixes an issue where excluded fields could overwrite calculated fields 
+- Fixes an issue where excluded fields can overwrite calculated fields 
   with the same name.
 - Fixes an issue where calculated fields based on decimal column values 
   return ``NaN``.